1. Field of the Invention
The present invention relates to a substrate rotating device and a manufacturing method and apparatus of a recording medium master.
2. Description of the Related Art
A variety of large-capacity recording media are under development for recording image/audio data and digital data thereon. An optical disc such as a DVD (Digital Versatile Disc) is one example of the recording media. Research and development are now under progress for increasing the recording capacity to, for example, 30 GB (Giga-Bytes) for the optical disc having a diameter of 12 cm. Also, a hard disk platter for magnetic recording having large capacity is also under development.
Recording resolution, however, is limited by the spot diameter of a laser beam for recording in the manufacturing process of a master (i.e., an original master or a stamper) of a recording medium using a conventional laser beam in a visible or ultraviolet wavelength range. Investigations have been made for manufacturing the master (i.e., cutting of the master) with a master manufacturing apparatus using an electron beam for increasing the recording density of the disc, since the electron beam has a smaller spot diameter than a visible or ultraviolet laser beam.
The manufacturing method of the master through exposure to the electron beam involves coating of a master-disc substrate (hereinafter, simply referred to as xe2x80x9csubstratexe2x80x9d) with an electron beam resist, and irradiating the substrate with the electron beam in a vacuum environment. The electron beam is applied to form a latent image of miniature patterns (i.e., electron beam exposure) in the electron beam resist. The substrate undergoes a development, patterning and removal processing of the resist, resulting in formation of miniature concave/convex patterns on the substrate.
For achieving a high resolution in the electron beam exposure, the electron beam must be converged into a thin beam which however travels at a higher velocity. A fast electron beam is hardly absorbed in an electron beam resist layer but pass therethrough, thereby resulting in a reduced amount of exposure and a lower resolution.
It is contemplated to perform a constant angular velocity exposure in the electron beam method in which exposure (i.e., recording) is performed on a substrate rotated at a constant rotating speed, because of its simple control feature for a substrate rotating system. However, the line velocity greatly varies depending on a radial position of the substrate when the substrate is rotated at a constant angular velocity for exposure. For example, when using a substrate in which a recording radial position varies in a range of 20 to 60 mm (electron beam irradiation range), the line velocity varies approximately three times.
It is therefore necessary to control the velocity of the electron beam in accordance with variations in the line velocity. For example, when the velocity of the electron beam is changed by changing an accelerating voltage applied to an electron gun, the beam diameter also changes simultaneously, resulting in variations in the size of recorded pits, the width of grooves and so on. Further, the axis and focus of the electron beam also fluctuate by changing the accelerating voltage applied to the electron gun. On the other hand, there is a method to use a condenser lens to control the amount of the electron beam current. However, there arises a problem that the structure of the electron beam irradiating system becomes complicated.
The electron beam is used in a vacuum atmosphere since the electron beam has properties of greatly diffusing and attenuating in an atmospheric pressure and the existence of another medium on a beam propagation path is not preferred. Consequently, the electron gun, a substrate rotating device, a substrate transporting device are all accommodated in a vacuum chamber and used in a vacuum.
The driving devices must be extremely accurately controlled for positioning and driving the substrate, since the master manufacturing apparatus forms a latent image of miniature concave/convex patterns at an extremely small pitch on the substrate.
The substrate must be rotated with high accuracy when manufacturing a high-density master disc in a master manufacturing apparatus using the electron beam.
Also, when the substrate is fixed by a mechanical chucking mechanism, the center of the substrate is susceptible to shifting, thereby causing a lower accuracy.
For recording (cutting) information on a substrate for an information recording medium, the substrate is placed on a turntable, and an electron beam is emitted from an electron beam irradiating means to irradiate the surface of the substrate with the electron beam. In this event, since an electromagnetic motor is used as a substrate rotating device for applying the turntable with a rotating force, an electromagnetic field is generated near the motor. The electromagnetic field, however, adversely affects a direction of the emitted electron beam, thereby reducing a recording or cutting accuracy.
To solve this problem, there is disclosed in Japanese Patent No. 3040887 (Japanese Unexamined Patent Publication Kokai No. H06-131706), a master manufacturing apparatus in which an electromagnetic motor is surrounded by a magnetic shielding means in order to avoid the influence of an electromagnetic field generated by the motor to the electron beam.
In a substrate rotating device of a conventional master manufacturing apparatus, a spindle shaft is supported by a static pressure air bearing in a housing, and rotated by a motor. A magnetic fluid seal is provided in a gap along the radial direction between the housing and the spindle shaft for blocking air for the bearing from a vacuum chamber.
In the conventional substrate rotating device, heat generated from a magnetic fluid seal and a motor transfers to a spindle shaft and its surroundings when it is used at a high rotational speed. The heat thus generated causes the spindle shaft to expand thermally and the shaft length to change. This results in a change in the height of a turntable attached on the shaft for carrying the substrate, leading to unstable focusing of an electron beam which should be converged on the substrate. In addition, the temperature distribution fluctuates in the magnetic fluid, causing unstable rotation of the spindle shaft. Consequently, the recording accuracy is deteriorated such as variations in track pitch of a resulting master and an increased amount of jitter in a reproduced signal.
Likewise, miniature patterns are formed through exposure of an electron beam or direct drawing with the electron beam in the manufacturing process of a master for magnetically recording hard discs. The rotation driving system and electron beam must be controlled with high accuracy in the manufacturing process of the master for forming miniature patterns using the electron beam.
The present invention is made in view of the problems mentioned above, and the object of the present invention is to provide a highly-accurate substrate rotating device, and a master manufacturing apparatus and a method which are capable of manufacturing a high-density master disc.
It is another object of the present invention to provide a substrate rotating device which suppresses the influence of variations in temperature during driving, and a master manufacturing apparatus using the same.
To achieve the object, according to one aspect of the present invention, there is provided an apparatus for manufacturing a master of a recording medium by irradiation of an electron beam on a substrate placed on a turntable disposed within a chamber, which comprises an electron-beam emitting portion for emitting the electron beam; an electron-beam converging portion for converging the electron beam; a retarding voltage applying portion for applying the substrate with a retarding voltage having a magnitude of decelerating electron rays of the electron beam; and a vacuum atmosphere producing portion for evacuating the chamber to produce a vacuum atmosphere therein.
According to another aspect of the present invention, there is provided an apparatus for manufacturing a master of a recording medium by irradiation of an electron beam on a substrate, which comprises an electron-beam emitting portion for emitting the electron beam; an insulating turntable for supporting the substrate on a supporting surface thereof, the turntable having a throughhole; a spindle housing; a spindle shaft rotatably supported by the spindle housing through an air bearing, and having one end fixed to the turntable; a motor for rotating the spindle shaft; and an electron beam decelerating portion for applying the substrate with a retarding voltage of a magnitude of decelerating the electron beam, wherein the electron beam decelerating portion includes a conductive member which is urged such that the conductive member can project and retract from and into the supporting surface through the throughhole of the turntable, and a relay portion for relaying the retarding voltage to the conductive member through a rotary connector.
According to another aspect of the present invention, there is provided a substrate rotating device which comprises an insulating turntable for carrying a substrate thereon; a spindle housing; a spindle shaft rotatably supported by the spindle housing through an air bearing and having one end fixed to the turntable; a motor for rotating the spindle shaft; and an electrostatic chucking portion for attracting the substrate to the turntable, wherein the electrostatic chucking portion includes a chucking electrode disposed in the turntable, a power supply cable for supplying a chucking voltage to the chucking electrode through the spindle shaft, and a rotary connector for supplying the chucking voltage to the power supply cable.
According to another aspect of the present invention, there is provided an apparatus for manufacturing a master of a recording medium by irradiation of an electron beam on a substrate, which comprises an electron-beam emitting portion for emitting the electron beam; a substrate rotating device including an insulating turntable for supporting the substrate on a supporting surface thereof, the turntable having a throughhole, a spindle housing, a spindle shaft rotatably supported by the spindle housing through an air bearing and having one end fixed to the turntable, and a motor for rotating the spindle shaft; a translation driving portion for translating the rotation driving portion relative to the electron-beam emitting portion; and an electrostatic chucking portion for attracting the substrate to the turntable, wherein the electrostatic chucking portion includes a chucking electrode disposed in the turntable, a power supply cable installed in the spindle shaft for supplying a chucking voltage to the chucking electrode, and a rotary connector for supplying the chucking voltage to the power supply cable.
According to another aspect of the present invention, there is provided an apparatus for manufacturing a master of a recording medium by irradiation of an electron beam on a substrate placed on a turntable disposed in a chamber, which comprises an electron beam emitting portion for emitting the electron beam; an electron beam converging portion for converging the electron beam; an electron beam decelerating portion for applying the substrate with a retarding voltage of a magnitude of decelerating the electron beam; and a vacuum atmosphere producing portion for evacuating the chamber to produce a vacuum atmosphere therein, wherein the turntable has an adjacent region adjacent to an outer edge of the substrate placed on the turntable and the adjacent region has a predetermined resistance value lower than the vacuum atmosphere.
According to another aspect of the present invention, there is provided an apparatus for manufacturing a master of a recording medium by irradiation of an electron beam on a substrate placed on a turntable disposed in a chamber, comprising: an electron-beam emitting portion for emitting the electron beam; an electron-beam converging portion for converging the electron beam; a retarding voltage applying portion for applying the substrate with a retarding voltage of a magnitude of decelerating the electron beam; a vacuum atmosphere producing portion for evacuating the chamber to produce a vacuum atmosphere therein; and an adjacent ring having a predetermined resistance value lower than the vacuum atmosphere and adjoining to the substrate placed on the turntable.
According to another aspect of the present invention, there is provided a method of manufacturing a master of a recording medium by irradiation of an electron beam on a substrate placed on a turntable disposed in a chamber, which comprises the steps of evacuating the chamber to a vacuum; applying a substrate placed on the turntable with a retarding voltage of a magnitude of decelerating the electron beam; and converging the electron beam to irradiate the substrate with the converged electron beam.
According to another aspect of the present invention, there is provided an apparatus for manufacturing a master by irradiation of an electron beam on a substrate having a resist formed on a principal surface thereof, which comprises an electron gun; an accelerating voltage applying portion for applying the electron gun with an accelerating voltage to emit an electron beam; a rotation driving portion for rotating the substrate substantially at a constant angular velocity; a movement driving portion for relatively moving an irradiation position of the electron beam in a rotational radial direction of the substrate; an electron beam decelerating portion for applying the substrate with a retarding voltage having a magnitude of decelerating electron rays of the electron beam; and a controller for varying the electron beam retarding voltage in accordance with the irradiation position of the electron beam in the rotational radial direction of the substrate while maintaining the accelerating voltage substantially constant.
According to another aspect of the present invention, there is provided a substrate rotating device comprising a housing, a spindle shaft accommodated in the housing with one end thereof exposed from the housing, the spindle shaft being rotatably supported by a bearing, a motor for driving the spindle shaft, and a magnetic fluid seal intervening between the housing and the spindle shaft, the substrate rotating device for use in a vacuum atmosphere, which comprises temperature sensors and electric heaters disposed near the magnetic fluid seal and the motor; and a temperature controller for controlling the electric heaters based on outputs of the temperature sensors.
According to another aspect of the present invention, there is provided a master manufacturing apparatus using a substrate which comprises a substrate rotating device for rotating the substrate; an electron beam emitting portion including a deflecting portion for controlling deflection of an electron beam and a focus control portion for converging the electron beam to irradiate a principal surface of the substrate with the converged electron beam; and a movement driving portion for relatively moving the substrate rotating device and the electron beam emitting portion in a radial direction of the substrate, wherein the substrate rotating device has a housing; a spindle shaft accommodated in the housing with at least one end thereof exposed from the housing and rotatably supported by a static pressure air bearing; a motor for rotating the spindle shaft; a magnetic fluid seal intervening in a gap between the housing and the spindle shaft; temperature sensors and electric heaters disposed near the magnetic fluid seal and the motor; and a temperature controller for controlling the electric heaters based on the outputs of the temperature sensors.